A conventional porous carbon is still a very promising material for the removal of gaseous pollutants because of its abundant surface functional groups and a high specific surface area. Here, we prepared an environment-friendly uniform N-rich narrow micropore activated carbon, for the removal of formaldehyde, based on steam activation and N-rich with chitin as the starting material. A sample carbonized at 500 °C and steam activated at 800 °C (CAC800) showed a reasonable yield (55%) with uniform and narrow micropores without mesopores but having a balanced nitrogen functionality. CAC800 possesses outstanding formaldehyde removal capabilities under both dry and wet (humidity 45%) conditions. In addition, when compared with commercial activated carbon materials, we clearly demonstrated that the existence of high nitrogen content with uniform and narrow micropores simultaneously removed formaldehyde, effectively.

Though many treatment technologies of contaminated water have been developed for a long time, it is still difficult to find a suitable method for large volumes of low radioactivity tritium-contaminated water. For this reason, most of the tritium-contaminated water been discharged to the biosphere or been stored in a special control area as radioactive waste. Activated carbon is a common material, but since there are few data on the treatment of tritium-contaminated water, its adsorption behavior to HTO is worth studied. In our study, for the tritium-contaminated water having a low radioactivity concentration (350-480 Bq/g), adsorption experiments were performed with activated carbon. The effects on the selective adsorption of HTO were investigated for temperature (5-55°C), hydrogen peroxide (1-10wt%) and activated carbon reuse (1-6 times) under non-equilibrium conditions. The treatment of activated carbon significantly reduced the radioactivity of tritium-contaminated water around 60 minutes of adsorption time. In order to clearly analyze the experimental results, positive factors and negative factors on the HTO selectivity were separately evaluated according to the adsorption time. Temperature and the reuse of activated carbon were evaluated as negative factors for HTO selectivity of activated carbon, whereas hydrogen peroxide (> 5wt%) was evaluated as a positive factor. By the evaluation method of separating the influencing factors into two types, the adsorption experimental results of HTO could be understood more clearly.

In NPP (nuclear power plant), boric acid is used as a neutron absorbent. So radioactive boric acid waste are generated from various waste streams such as discharge or leakage of reactor coolant water, floor drains, drainage of equipment for operation or maintenance, reactor letdown flows and etc. Depending on KHNP, 20,015 drum (200 L drum) of concentrated boric acid waste were stored in KOREA NPP until 2019. In previous study, our group suggested the waste up-cycling process synthesizing B4C neutron absorber using boric acid waste and activated carbon waste to innovatively reduce radioactive wastes. Radioactive activated carbon waste was utilized in off gas treatment system of NPP to capture nuclide such as I-131, C-14 and H-3. Activated carbon waste is treated as low-level radioactive waste and pre-treatment system for removing nuclide from the activated carbon waste is needed to use B4C up-cycling process. In this study, microwave treatment system is suggested to treat the activated carbon waste. Activated carbon waste was exposed to microwave for a few minutes and temperature of the waste was dramatically increased over 400°C. Nuclide in the activated carbon waste were selectively removed from the waste without massive production of secondary off gas waste.

This study investigates the preparation of activated carbon fiber derived from waste cotton fabric for economical and ecofriendly recycling as well as its application to water purification. The activated carbon fiber was prepared by physical activation using steam and the adsorption property was then evaluated using methylene blue. When the activation temperature increased, the specific surface area and mesopore volume of the activated carbon fiber increased up to 2562 m2/ g and 0.214 cm3/ g, resulting in the increased adsorption of methylene blue. The results of the adsorption experiment for the activated carbon fiber were analyzed using the Langmuir and Freundlich equations. The Langmuir equation was more suitable than the Freundlich equation to explain the adsorption equilibrium. The maximum adsorption amount of methylene blue was 161.1–731.5 mg/g for fiber samples activated at temperatures ranging from 750 to 950 °C with sample labeled 750SA to 900SA according to the Langmuir equation. The kinetics of methylene blue adsorption by the activated carbon fiber were analyzed using non-linear pseudo-first-order and pseudo-second-order. Sample 750SA was suitable for the pseudo-first-order and 800SA, 850SA, and 900SA sample were suitable for the pseudo-second-order. Therefore, waste cotton fabric has the potential to be the precursor for activated carbon fiber with excellent adsorption properties.

In preparation of porous carbon materials microwave oven brightening is one of the warming modes used ever. The various procedures that take place in microwave combustion process include carbonization, incitation, and recovery and thus carbon is defined. This paper compares ideal conditions of traditional warming methods, as well as their implementation potential, losses, and specifications. This porous carbon with heat treatment possesses various properties and they are well suited for energy applications which require constrained space such as hydrogen storage in solid-state and supercapacitors. The enhanced properties are chemical and thermal stability, ready availability, low framework density and ease of processability. The recent trend in class of porous carbons is Activated Carbons that are employed traditionally as adsorbents or catalyst supporters but currently, they found potent applications in fabricating for hydrogen storage materials and supercapacitors. These activated carbons are much enhanced form in class of porous carbon materials and they possess the capability to enable hydrogen economy, where the energy carrier is hydrogen. Therefore, the utility of activated carbons as a source for energy storage experiences a rapid growth at current trend and they possess significant advances. This investigation is based on detailed cost development data and electrical imperativeness applications.

There is a need for the purification of indoor air owing to a high rate of pollution in today’s world. For this, cabin air filters (CAFs) are widely used, which requires the addition of certain adsorbents to increase the volatile organic compound (VOC) removal efficiency. However, this addition causes high-pressure resistance, which may hamper commercial applications by requiring more energy and negatively affecting fresh air delivery rate. Hence, in this study, a high-performance combined CAF (CCAF) with excellent dust and chemical filtration performance and low differential pressure was prepared using granular activated carbon (GAC)/activated carbon fiber (ACF) mixed medium. The GAC/ACF mixed medium had higher air permeability than the ACF medium of the same weight, and it exhibited similar ultrafine dust filtration performance to the ACF medium without an increase in differential pressure. In addition, the GAC/ACF mixed medium showed excellent gas removal performance without increasing differential pressure by combining the VOC removal characteristics of the GAC and ACF filter media. The improved VOC removal performance of the GAC/ACF mixed medium was due to the hybrid effect of the hierarchical pore structures of the GAC and the nearly uniform pore structures of the ACF, which resulted in a slow and increased gas adsorption by the GAC and rapid gas adsorption of the ACF.

The electrochemical capacitive properties of biomass-derived activated carbons are closely dependent on their microscopic structures. Here, activated carbon fibers (ACFs) were prepared from natural cattail fibers by carbonization and further chemical activation. The activation temperature affected on the microscopic structures and electrochemical properties of the activated carbon fibers. The results show that the optimum activation temperature is 800 °C. And the as-prepared ACF- 800 possesses high micropore specific surface area of 710.4 m2 g− 1 and micropore volume of 0.313 cm3 g− 1, respectively. For supercapacitor applications, the ACF-800 displays a high specific capacitance of 249 F g− 1 at a current density of 0.05 A g− 1, excellent rate performance and cycle stability in a three-electrode system. The excellent electrochemical performance indicated that the obtained activated carbon fibers could be a promising electrode material in supercapacitor.

In view of the activated carbon pore-forming mechanism, the fractal hypothesis of pore interior growth was proposed by optimizing the structure of Sierpinski sponge. Based on the hypothesis and the definition of fractal dimension, the function relationship between the reaction degree, reaction step length, specific surface area and pore volume was deduced, and the pore fractal growth model of activated carbon activation process was established. Semi-coke, apple charcoal and lychee charcoal were used to prepare activated carbon. The pore size distributions of the activated carbons are in accordance with the fractal growth hypothesis. Further, the reaction degree and reaction step length can be determined by the experimental data of pore and surface structure, which verified the feasibility of the pore fractal growth model.

In this study, the removal efficiency of PFCs(perfluorinated compounds) in the GAC(granule activated carbon) process based on the superheated steam automatic regeneration system was investigated in laboratory scale and pilot-scale reactor. Among PFCs, PFHxS(perfluorohexyl sulfonate) was most effectively removed. The removal efficiency of PFCs was found to be closely related to the EBCT, and the removal efficiencies of PFOA(perfluorooctanoic acid), PFOS(perfluorooctyl sulfonate), and PFHxS were 43.7, 75, and 100%, respectively, under the condition of EBCT of 6 min. Afterward, PFOA, PFOS, and PFHxS exhibited the earlier breakthrough time in the order. After that, GAC was regenerated, and the removal efficiency of the PFCs before and after regeneration was compared. As a result, it was shown that the PFCs removal efficiency in the regenerated GAC process were higher, and that of PFOA was improved to 75%. The findings of this study indicate the feasibility of the superheated steam automatic regeneration system for the stable removal of the PFCs, and it was verified that this technology can be applied stably enough even in field conditions.

By polymerizing acrylonitrile in the presence of ammonium persulfate as an initiator and Pterocladia capillacea-activated carbon (P-AC) as a filler, a composite material polyacrylonitrile/Pterocladia capillacea-activated carbon (PAN/P- AC) was developed. By reacting hydroxylamine with the composite's nitrile groups, the prepared composite was functionalized by amidoximation. FTIR spectrometry, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET) analysis were all applied to thoroughly characterize the fabricated adsorbent. For the treatment of Cr(VI) ions from synthetic solutions, the adsorption properties of amidoximated polyacrylonitrile/Pterocladia capillacea-activated carbon (PAO/P-AC) were investigated. The pH effect, uptake kinetics, adsorption isotherms, and thermodynamics studies were used to characterize adsorption properties. As a kinetic model analysis, the data confirmed that the pseudo-second-order rate equation matched well the adsorption process. With coefficients of determination (R2) of 0.9998, the Tempkin isotherm model had the lowest error, suggesting that it is the best fitted model to describe this adsorption mechanism. Thermodynamic parameters demonstrated that Cr(VI) adsorption was endothermic.

Heavy metal pollution has a harmful impact on human health and is regarded as a vital problem. Preparation of a novel, low cost bio-sorbent for heavy metal sorption is the main target of this research. Non-living Chlorella Vulgaris Alga/Date pit activated carbon composite (1:1), (CV/AC), is a novel bio-sorbent prepared by the wet-chemical method for sorption of Pb (II) and Sr (II) from aqueous media. The optimum pH for sorption reaction is 5 and the equilibrium time is achieved within 1 h. The sorption efficiencies are 90.5% for Pb(II) and 95.7% for Sr(II) with initial concentration Co 10 mg L– 1 at 298 K. The monolayer sorption capacities of CV/AC composite at 298 K and pH = 5 were 6.34 ± 0.059, 5.97 ± 0.22 mg g– 1. The saturation capacities were 98.5 and 125 mg g– 1 for Pb (II) and Sr (II), respectively after 10 days. The sorption process is a spontaneous and endothermic reaction. It follows a pseudo-2nd-order mechanism. The results are suggestive of the need to adopt CV/AC composite as a potential bio-sorbent of Pb (II) and Sr (II) for waste water treatment.

Abstract Recently, the circular economy aiming at elimination of waste and the continual use of resources has attracted a lot of attentions. In the circular system, the resource recovery uses the recycled wastes as the raw material to manufacture new valuable products. This work focuses on a low-cost process, in which an activated carbon (AC) adsorbent was prepared from waste cation exchange resin by calcination and HNO3 activation hydrothermal method. Surface structure and chemistry of AC were characterized by SEM, XRD, FTIR and Boehm titration. It was found that the acid treatment could increase the number of pores and the content of oxygen-containing functional groups on AC surface. In the adsorption experiment, Methylene blue (MB) was used to assess the adsorption capacity of AC. Experimental results showed that the highest efficiency of MB removal was achieved by AC with modification of 4M HNO3, showing the acidification effect on the adsorption capacity of AC. Adsorption isotherms of Langmuir and Freundlich were employed to fit the experimental data. It was shown that MB adsorption on AC is more consistent with Langmuir model that assumes a homogeneous adsorption. In the adsorption kinetic analysis, the adsorption was found to follow the pseudo-second-order model, indicating that adsorption of MB on acidified AC is dominated by chemical adsorption. The study revealed that the waste ion-exchange resin is a proper precursor of carbon adsorbent for MB dye. This low-cost method would specifically reduce the environmental cost of waste disposal.

The production of macroalgae-derived adsorbent is of great importance to realize the idea of treating pollutants with invaluable renewable materials. Herein, a novel meso-micro porous nano-activated carbon was prepared from green alga Ulava lactuca in a facile way via chemical activation with zinc chloride. The resultant activated carbon possesses a significant specific surface area 1486.3 m2/ g. The resulting activated carbon was characterized and investigated for the adsorption of Direct Red 23 (DR23) dye from an aqueous environment. Batch method was conducted to study the effects of different adsorption processes on the DR23 dye adsorption from water. Isotherms and kinetics models were investigated for the adsorption process of DR23 dye. It was found that the adsorption data were well fitted by Langmuir model showing a monolayer adsorption capacity 149.26 mg/g. Kinetic experiments revealed that the adsorptions of DR23 dye can be described with pseudo-secondorder model showing a good correlation (R2 > 0.997). The prepared activated carbon from Ulava lactuca was exposed to a total of six regeneration experiments. The regeneration result proved that the fabricated activated carbon only loses 19% of its adsorption capacity after six cycles. These results clearly demonstrated the high ability of the obtained active carbon to absorb anionic dyes from the aqueous environment.

The pore structure of pitch-based activated carbon prepared by physical activation was improved by nitric acid treatment of pitch. The nitric acid treatment introduced oxygen and nitrogen functional groups on pitch, and increased pitch molecular weight by cross-linking. The introduced oxygen and nitrogen functional groups on pitch were removed during the carbonization process, so they did not directly affect the physical activation process. The increased pitch molecular weight induced an increase of the pitch softening point. The increased softening point prevented rearrangement between the pitch molecules during the carbonization process, thereby inhibiting the orientation improvement of pitch molecules. The crystal degree of the carbonized pitch was reduced due to the inhibition of the orientation improvement. The reduced crystal degree increased reactivity between carbonized pitch and activation agent ( CO2) and formed micropores, so that activated carbon with a high specific surface area could be prepared.

The present study analyzed the pore formation and development process in carbon black that was activated by CO2 gas and the effect of the burn-off (BO) ratio on the process, particularly based on changes in the surface shape and internal microstructure. The activation process was performed as follows. Carbon blacks were injected into a horizontal tube furnace when the inside temperature reached 1000 °C. Carbon black samples with different BOs, i.e., 7.2%, 15.4%, 30.4%, 48.2%, 59.9%, and 83.2%, were prepared by varying the activation time. The microstructure of the activated samples was observed and examined using SEM and TEM. The results showed that pore passages were first created on the surface of the primary particles of the carbon black, and then the inner portion of the carbon black with a lower degree of crystallinity started to be activated, thereby causing inner pores to be formed. These inner pores then started to grow and coalesce into larger pores, thereby causing the crystallite layers in the inner portion of the carbon black to be activated. The changes in the microstructure of the carbon black during the activation reaction were attributable to the carbon black manufacturing process, in which the nucleation and growth of the primary particles of the carbon black occurred within a very short period of time. Thus, the crystallization of the inner portion was suppressed, and therefore, the degree of crystallinity was lower in the inner portion than in the outer portion.

Global warming and climate changes are the ultimate consequences of increased CO2 volume in the air. Physical activation was used to prepare high-throughput activated carbon from a low-cost date stone. The adsorption performance of activated carbon using fixed bed for CO2 separation was studied. The reliance of temperature, flow rate, and initial CO2 concentration levels on breakthrough behaviour was analysed. The adsorption response was explored in terms of breakthrough and saturation points, adsorption capacity, temperature profiles, utilization factor, and length of mass-transfer zone. Increased temperatures lead to vary the breakthrough periods notably. The vastly steep breakthrough curves reveal satisfactory utilization of bed capacity. LMTZ is varied positively with increased feed rates and temperatures. The high utilization factor of 0.9738 with 1.66 mmol/g CO2 uptake was acquired at 298 K and 0.25 bars. The findings recommend that the carbon prepared from date stone is encouraging to capture CO2 from CO2/ N2 mixture.

In view of the growing need for clean energy, supercapacitors (SC), especially those based on activated carbon (AC) and organic electrolyte are attracting great attention for their theoretically infinite life span. However, they still age much faster than expected due to certain mechanisms. Several researches is being conducted to understand these mechanisms, but so far, the chemical reactions at the phase boundary of the activated carbon electrodes and organic electrolyte have been very unclear. Some pathways have not yet been investigated; there is no research on the reactions that can take place between acetonitrile in the vapor phase and the oxides presented on the surface of activated carbons. For this reason, in this study, divided into two parts, the first based on a thermal simulation and the second based on an experimental study, we have systematically described the ageing mechanisms by determining the gas-phase reactions that can occur at the electrode–electrolyte interface. On the one hand, a thermal model of a supercapacitor cell using activated carbon and organic electrolyte technology has been developed. This model allowed us to study the temperature distribution of supercapacitors, and thus to determine the thermodynamic parameters related to the phenomena produced at the electrode–electrolyte interface. On the other hand, a thermo-gravimetric analysis coupled with gas phase infrared spectroscopy on the activated carbons of an aged supercapacitor of the same technology as that used in the simulation was carried out. The results obtained made it possible to identify the chemical groups produced by ageing.

Recently, activated carbon derived from different agricultural by-products or bio-waste is receiving a great deal of attention due to its low or zero cost and environmental friendliness. In this work, flowers obtained from Borassus flabellifer (BFL) is used as a carbon source and potassium hydroxide (KOH) as activation precursor to produce activated carbon with high specific surface area and predominant micropore. The obtained carbon material was activated at 650 °C. The as-prepared sample had a specific surface area of 930.3 m2/ g and pore size distribution of 1.96 nm. The carbon material exhibited high electrochemical performance with a specific capacitance of 247 F/g at 0.5 A/g in 1 M H2SO4 electrolyte and an excellent cycling stability of 94% after 2500 cycles. A specific energy of 101.1 Wh/kg and a specific power of 4500 kW/kg were obtained. Based on the electrochemical properties exhibited by BFL, it could be used as an excellent electrode material for supercapacitor applications.

Cost-effective and sustainable high-performance supercapacitor material was successfully prepared from cellulosic waste (Sapindus trifoliatus nut shells) biomass-derived activated carbon (CBAC) by physical activation method. The CBAC displays nanofiber morphology, high specific surface area (786 m2/ g), large pore volume (0.212 cm3 g− 1) which are evaluated using FESEM, BET and possessed excellent electrochemical behavior analyzed through various electrochemical methods. Moreover, the assembled symmetric CBAC//CBAC device exhibits high specific capacitance of 240.8 F g− 1 with current density of 0.2 A g− 1 and it is maintained to 65.6 F g− 1 at high current density of 2.0 A g− 1. In addition, the symmetric device delivers an excellent specific energy maximum of over 30 Wh kg− 1 at 400 W kg− 1 of specific power and excellent cycling stability in long term over 5000 cycles. The operation of the device was tested by light-emitting diode. Hence, CBAC-based materials pave way for developing large-scale, low-cost materials for energy storage device applications.